Astronomy Picture of the Day

   [1]Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                2019 July 21
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                       Moonquakes Surprisingly Common
                  Image Credit: [3]NASA, [4]Apollo 11 Crew

   Explanation: Why are there so many moonquakes? Analyses of
   [5]seismometers left on the moon by the [6]Apollo moon landings reveals
   a surprising number of [7]moonquakes occurring within 100 kilometers of
   the surface. In fact, 62 [8]moonquakes were detected in data recorded
   between 1972 and 1977. [9]Many of these moonquakes are not only strong
   enough to [10]move furniture in a [11]lunar apartment, but the stiff
   rock of the moon continues to vibrate for many minutes, significantly
   longer than the softer rock [12]earthquakes on [13]Earth. The cause of
   the moonquakes remains unknown, but a [14]leading hypothesis is the
   collapse of underground faults. Regardless of the source, [15]future
   moon dwellings need to be built to withstand the frequent shakings.
   [16]Pictured here 50 years ago today, [17]Apollo 11 astronaut [18]Buzz
   Aldrin stands beside a recently deployed [19]lunar seismometer, looking
   back toward the [20]lunar landing module.

                       Tomorrow's picture: moon circle
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    Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell
                                 ([35]UMCP)
          NASA Official: Phillip Newman [36]Specific rights apply.
              [37]NASA Web Privacy Policy and Important Notices
                A service of: [38]ASD at [39]NASA / [40]GSFC
                           & [41]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/1907/AldrinSeismometer_Apollo11_3000.jpg
   3. https://www.nasa.gov/
   4. https://www.hq.nasa.gov/office/pao/History/alsj/a11/a11.crew.html
   5. https://en.wikipedia.org/wiki/Seismometer
   6. https://nssdc.gsfc.nasa.gov/planetary/lunar/apolloland.html
   7. https://en.wikipedia.org/wiki/Quake_(natural_phenomenon)#Moonquake
   8. http://adsabs.harvard.edu/abs/2017PEPI..262...28G
   9. https://science.nasa.gov/science-news/science-at-nasa/2006/15mar_moonquakes
  10. https://www.youtube.com/watch?v=A75icqf9M6w
  11. http://spaceflight.nasa.gov/gallery/images/vision/lunar/ndxpage1.html
  12. https://earthquake.usgs.gov/learn/facts.php
  13. http://antwrp.gsfc.nasa.gov/apod/image/0208/earthlights02_dmsp_big.jpg
  14. http://adsabs.harvard.edu/abs/2017PEPI..262...28G
  15. https://apod.nasa.gov/apod/ap171025.html
  16. https://www.flickr.com/photos/nasacommons/9457418581/in/album-72157634973926806/
  17. https://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/
  18. http://en.wikipedia.org/wiki/Buzz_Aldrin
  19. https://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/pse/
  20. https://apod.nasa.gov/apod/ap030920.html
  21. https://apod.nasa.gov/apod/ap190720.html
  22. https://apod.nasa.gov/apod/archivepix.html
  23. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  24. https://apod.nasa.gov/apod/lib/aptree.html
  25. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  26. https://apod.nasa.gov/apod/calendar/allyears.html
  27. https://apod.nasa.gov/apod.rss
  28. https://apod.nasa.gov/apod/lib/edlinks.html
  29. https://apod.nasa.gov/apod/lib/about_apod.html
  30. http://asterisk.apod.com/discuss_apod.php?date=190721
  31. https://apod.nasa.gov/apod/ap190722.html
  32. http://www.phy.mtu.edu/faculty/Nemiroff.html
  33. http://www.phy.mtu.edu/
  34. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  35. http://www.astro.umd.edu/
  36. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  37. https://www.nasa.gov/about/highlights/HP_Privacy.html
  38. https://astrophysics.gsfc.nasa.gov/
  39. https://www.nasa.gov/
  40. https://www.nasa.gov/centers/goddard/
  41. http://www.mtu.edu/